This invention relates to solid state semiconductor electronic control devices having their most advantageous application as current or voltage amplifiers, but which can be used as logic circuit or switch elements, if desired.
More specifically, this invention relates to solid state semiconductor electronic control devices having certain advantages over junction transistors, such as greater amplification levels or minimum adverse affects from ionizing and neutron radiation. Since the electronic control devices of the invention operates on a principle similar to transistors, a brief explanation of transistor operation would be helpful in understanding the different forms of the present invention.
The most common form of solid state amplifier device is the junction transistor which commonly comprises a body of crystalline semiconductor material "doped" or alloyed with impurities which do not combine perfectly with the semiconductor lattice structure. Different regions or layers of the body of semiconductor material are doped with p or n type impurities which, respectively, provide the layers or regions involved with a majority of electrical charge carriers, respectively referred to as holes and electrons. A junction transistor generally has three contiguous layers or regions of doped semiconductor material of alternating type, to form a pnp type transistor or a npn type transistor (the letters p or n designating, respectively, hole and electron supplying impurities in the layer or region of the device involved). The junction between one of the outer layers (referred to as base) is coupled to a source of direct current voltage which forwarded biases the junction between these layers, so as to attract electrical charge carriers constituting the majority carriers of the emitter layer to the latter junction where the electrical charge carriers enter the base layer. The junction between the base and collector layers is generally back-biased by a source of direct current voltage. The thickness of the base layer is critical to the amplification action of a transistor device, and must act as a semiconductor insulator so as not to short circuit the emitter and collector layers and must be sufficiently thin that it is less than what is referred to as the diffusion length of electrical charge carriers therethrough. In other words, the base electrode-forming layer is made sufficiently thin that the electrical charge carriers injected thereinto from the emitter electrode are not neutralized or trapped before reaching the junction between the base and collector electrode-forming layers.